At least one MI6-run agent was aware of sexual abuse being committed in a notorious Belfast boys’ home, according to one of the agency’s historic intelligence documents.

A classified MI6 note containing the claim about the Kincora abuse scandal was presented in evidence as a senior ranking MI6 officer was questioned at Northern Ireland’s Historical Institutional Abuse (HIA) inquiry.

But the anonymised deputy director of the Secret Intelligence Service (MI6), referred to as officer A as he testified via video-link, rejected any suggestion his organisation was aware of the abuse.

He told the inquiry panel that an extensive trawl of MI6’s files could find no other documentary evidence to corroborate the 1989 note.

“We have found nothing that was written at the same time that justifies that assertion or nothing in our subsequent records that backs up that assertion,” he said.

Questioned by the inquiry chair, retired judge Sir Anthony Hart, whether the officer who wrote the note had perhaps not disclosed the information to colleagues or had simply “got the wrong end of the stick”, the MI6 officer replied: “I cannot speculate as to what he was thinking when he wrote it.”

The east Belfast home has long been at the centre of allegations that a paedophile ring involving high-profile political and military figures abused young residents in the 1970s.

There are associated claims that the UK’s intelligence agencies covered up the abuse in order to exploit the perpetrators for information gathering purposes.

MI6 is primarily involved in intelligence operations overseas but the agency worked in Northern Ireland during the 1970s providing support to its domestic counterpart MI5.

The document laid before the HIA, sitting in Banbridge Courthouse, Co Down, suggested the need to carry out further research into the allegations surrounding Kincora.

The note stated: “We certainly ran at least one agent who was aware of sexual malpractice at the home and who may have mentioned that to his SIS (MI6) or Security Service (MI5) case officer.”

The document said the information was not pursued at the time as it was not of operational interest.

Three workers at the home were convicted and jailed in 1981 for abusing boys in their care but there have been persistent allegations that senior establishment figures were also involved in the crimes - with claims the intelligence agencies knew this and used it to their advantage.

Officer A insisted MI6 was not even aware the abuse was being committed

“I want to emphasise that the SIS does not exploit children or vulnerable adults,” he said.

The high-ranking SIS witness said if any MI6 officer had been involved in such activity they would have been dealt with “very seriously indeed”.

The HIA is examining allegations of child abuse in children’s homes and other residential institutions in Northern Ireland from 1922 to 1995.

The officer was also questioned about historic media claims about former MI6 chief Sir Maurice Oldfield.

Sir Maurice retired as MI6 director in the late 1970s but returned to intelligence work in 1979 when he was asked to become co-ordinator of security operations in Northern Ireland.

A year later, his security clearance was suddenly removed when it emerged he was gay. At the time the SIS would not give clearance to gay men, amid fears that foreign spies would try to blackmail them with the information.

He died in 1981 and months later a newspaper linked him to the abuse scandal at Kincora.

None of the former Kincora residents who have given evidence to the HIA have claimed Sir Maurice abused them. One has claimed they once saw him in the home.

Officer A told the inquiry that MI6 had identified no information to substantiate the allegations in regard to Sir Maurice.